Note 9 overhearting

Note 9 overhearting

So I have a thick clear otterbox case on my brand new Galaxy Note 9 Cloud Silver Edition that I bought at the beginning of December. The sides of the case from the middle of the phone down to the bottom are a burnt color. It is a dark burnt color closer to the charging port hole. I never mess with my phone while it is charging, and I use only the original C charger that it came with. I have noticed it get hot but I am not heavily on it a lot. Is there anything I can do or is this a sign that it could get way to hot and lead to a fire or worse?